Powdery polyether carboxylate-based polymeric compositions

ABSTRACT

A description is given of pulverulent polymer compositions based on polyether carboxylates, which are characterized in that they comprise 
     a) from 5 to 95% by weight of a water-soluble polymer made up of polyoxyalkylene-containing structural units, carboxylic acid and/or carboxylic anhydride monomers and, if desired, further monomers, and 
     b) from 5 to 95% by weight of a finely divided mineral support material having a specific surface area of from 0.5 to 500 m 2 /g (determined by the BET method in accordance with DIN 66 131). 
     These pulverulent polymer compositions, which can contain up to 90% by weight of polyether carboxylate, have a significantly increased sticking and caking resistance compared to spray-dried products and have further advantages when they are used in cement-containing building material mixtures.

DESCRIPTION

The present invention relates to pulverulent polymer compositions basedon polyether carboxylates, processes for preparing them and their use.

Water-soluble polymers comprising polyoxyalkylene-containing structuralunits, carboxylic acid and/or carboxylic anhydride monomers and, ifdesired, further monomers, hereinafter referred to as polyethercarboxylates, have recently found uses in a variety of applications.

Apart from their use as dispersion stabilizer in the preparation ofwater-soluble copolymers (WO 97/30 094), their use as protective colloidin the production of caking-resistant dispersion powders has beendescribed. However, polyether carboxylates are preferably used inbuilding materials such as concrete, mortars, bitumen, knifing fillers,adhesives, pigment-containing paints and coating compositions, inceramic compositions, in the refractories industry and petroleumprocessing to exert a targeted influence on the rheological and/orwetting properties of these building materials. Adsorptive interactionswhich polyether carboxylates can undergo with the hydraulic binderparticles of these building materials (cement, lime, calcium sulfate,etc.) result in stabilization of the mineral particles combined withreduced internal friction and thus in improved flow and processingproperties. Although these polymers consist of only two significantstructural units, namely a polyoxyalkylene-containing unit and acarboxylic acid(anhydride) monomer, a large number of types of linkageare possible. The structural variety of such polyether carboxylatesextends from random, alternating or block polymers through to combpolymers having carboxyl groups in the main chain and polyether units inthe side chain. Also included are graft copolymers which are formed byfunctionalization of polyethers by means of monomers containingcarboxylic acid groups.

Finally, the group of polyether carboxylates also includes polyesterswhich are formed by reaction of polyethers, such as polyethylene glycol,with polybasic carboxylic acids or carboxylic anhydrides. It isimmaterial whether these polymers are present as the free acid or intheir salt form.

The technical advantage of such products as fluidizers in cement-basedbuilding materials is, firstly, that long-lasting processability asdesired by the concrete transport industry can be achieved with use ofextremely small amounts. Secondly, these additives enable the proportionof water to be reduced so greatly that it is possible to producehigh-strength concrete which can be removed from the mold or from whichthe shattering can be removed after only 12 hours, thus meeting acentral requirement of the prefabricated parts industry. In addition,the polymers are free of toxicologically problematical constituents suchas formaldehyde, which distinguishes them from conventional cement flowimprovers, e.g. as disclosed in EP-B 214 412 or DE-C 16 71 017. For aseries of applications, it is useful and desirable to provide thewater-soluble polyether carboxylates in the form of their aqueoussolutions.

However, the use of aqueous preparations can be completely ruled out inother fields of application where the polymers are required as additivesin factory-produced dry mixes.

Apart from logistic and economic advantages (transport of water!),powders have a number of technical advantages over aqueous preparations.Stabilization against attack by microorganisms by means of addition ofbiocides becomes unnecessary as do the sometimes complicated measuresfor tank hygiene. Since polyether carboxylates can, owing to theirsurface-active properties, introduce undesirably high proportions of airinto the building material, antifoams are generally mixed into theaqueous preparations after they have been prepared.

Owing to the incompatibility of the antifoam in the aqueous medium ofthe polyether carboxylate, sedimentation and/or flotation phenomenaoccur, which leads to considerable problems at the end user.

If the polyether units in the polyether carboxylates are incorporated inthe main chain or bound as side chain constituents on the main chain viaester groups, undesirable hydrolysis with destruction of the polymerstructure can occur already during storage of the aqueous preparations.

This problem can be countered only “symptomatically” by storage at lowtemperatures, which greatly restricts the use of such aqueouspreparations, particularly in hot climatic zones. In addition to theunsatisfactory stability at temperatures above 30° C., there is thesensitivity to frost. Owing to the abovementioned facts, the use ofpowders has always been found to be preferable to the use of aqueouspreparations.

According to the prior art, polymer powders based on polyethercarboxylates are obtained by spray drying the aqueous preparations in astream of hot air, during which antioxidants and spray-dryingauxiliaries are advantageously added so as to

a) prevent spontaneous heating or spontaneous ignition of such polymersduring and after the drying process and

b) inhibit adhesion of the wax-like polymer particles in the dryer.

Neglect of the safety risks mentioned under a) has in the past led tofires during the spray drying process. Furthermore, despite the use ofspray-drying auxiliaries, it is sometimes difficult to isolate anon-sticky and caking-resistant polymer powder, especially when theproportion of polyether in the polymer is high and the proportion ofcarboxyl groups is low. These disadvantages, the high energy requirementfor spray drying and the emission limits to be adhered to during spraydrying are particularly serious.

The procedure in which the polyether carboxylate is firstly produced ina solvent-free polymerization, diluted with water and subsequentlyneutralized is particularly uneconomical. After that, spray drying iscarried out with the abovementioned disadvantages in order to remove thewater introduced in the dilution process.

It is therefore an object of the present invention to providepulverulent polymer compositions based on polyether carboxylates whichavoid the disadvantages of the prior art, i.e. give products which arestorage-stable at high temperatures and are also insensitive to frost,require no preservatives, are stable to spontaneous ignition and thermaloxidative degradation, give sticking- and caking-resistant powders andare obtainable at a low energy consumption and by a rational process.

According to the invention, this object is achieved by pulverulentpolymer compositions comprising

a) from 5 to 95% by weight of a water-soluble polymer made up ofpolyoxyalkylene-containing structural units, carboxylic acid and/orcarboxylic anhydride monomers and, if desired, further monomers, and

b) from 5 to 95% by weight of a finely divided mineral support materialhaving a specific surface area of from 0.5 to 500 m²/g (determined bythe BET method in accordance with DIN 66 131).

It has surprisingly been found that the incorporation of the polyethercarboxylates (component a) into the mineral component b) can be made soeffectively that up to 90% by weight of active ingredient, i.e. thepolyether carboxylate component, in the polymer composition can beachieved.

In addition, it was particularly surprising that the sticking and cakingresistance was considerably increased compared to spray-dried productsand additional advantages were found in the use of the compositions incement-containing building material mixtures.

The water-soluble polymers used for preparing the polymer composition ofthe invention are products which contain polyoxyalkylene groups,preferably polyethylene glycol or polypropylene glycol groups, in themain chain or in the side chain and additionally comprise carboxylicacid and/or carboxylic anhydride monomers, preferably acrylic acid,methacrylic acid, maleic acid, maleic anhydride, fumaric acid, itaconicacid and itaconic anhydride. Further monomers based on vinyl or acrylategroups can additionally contribute to making up the polyethercarboxylates. Examples of such further monomers are styrene,α-methylstyrene, isobutene, diisobutene, cyclopentadiene, ethylene,propylene, isoprene, butadiene, acrylonitrile, chloroprene, vinylacetate, N-vinylpyrrolidone, methyl acrylate, methyl methacrylate,n-butyl acrylate, 2-ethylhexyl acrylate, acrylamide, methacrylamide,acrylamidomethylpropane-sulfonic acid, styrenesulfonic acid, vinylchloride, methyl vinyl ether, ethyl vinyl ether, allyl alcohol,allylsulfonic acid, allyl chloride and others.

The polymers can be linear, have short-chain branching, have long-chainbranching or be crosslinked and can have comb structures, starstructures, dumb-bell structures and other morphologically conceivablestructures.

Examples are block copolymers of polymethacrylic acid and polyethyleneglycol, comb-like polymers having a polymethacrylic acid main chain andindividual polyethylene oxide side chains bound via ester groups, maleicanhydride/styrene copolymers partially esterified withmethylpolyethylene glycol, allylpolyethylene glycol/maleic acidcopolymers, vinylpolyethylene glycol/maleic monoester copolymers, graftcopolymers comprising a polyethylene glycol or polypropylene glycolskeleton and maleic anhydride or acrylic acid side chains which may inturn be esterified or partially esterified.

Polyesters, polyamides and polyurethanes which are based on alkyleneoxides such as ethylene oxide, propylene oxide or butylene oxide andbear ionic groups and are therefore water-soluble are also possible.

These polyether carboxylates can be in the form of their free acids orin neutralized form and can be prepared by solution polymerization, bulkpolymerization, inverse emulsion polymerization or suspensionpolymerization.

In preferred embodiments, polyether carboxylates prepared by bulkpolymerization are used. In the case of these, the usefulness of theinvention is particularly high since in the prior art these firstly haveto be diluted with water, neutralized and subsequently subjected tospray drying to remove the previously introduced water and convert theminto a powder.

It is an essential aspect of the invention that the finely dividedmineral support materials used have a specific surface area of from 0.5to 500 m²/g (determined by the BET method in accordance with DIN 66131). The proportions by weight of support materials in the pulverulentpolymer compositions depend on the type of polymer, its composition andthe form in which it is incorporated and also on the specific surfacearea and the adsorption capacity of the mineral support material. Theycan therefore vary within a very wide range from 5 to 95% by weight.

The type of these support materials is subject to no particularrestriction. It is important that the material is readily compatiblewith the polyether carboxylate, does not have an adverse effect on theaction of the polymer and even in small amounts gives pulverulentsticking- and caking-resistant polymer compositions.

Preference is given to using chalk, silica, calcite, dolomite, quartzflour, bentonite, ground pumice, titanium dioxide, fly ash, cement(Portland cement, blast furnace cement, etc.), aluminum silicate, talc,anhydrite, lime, mica, kieselguhr, gypsum, magnesite, alumina, kaolin,ground slate and other rocks, barium sulfate and also mixtures of thesematerials. According to a preferred embodiment, the mineral supportmaterial already comprises one or more mineral components of a buildingmaterial.

The finely divided support materials have a preferred particle size offrom 0.1 to 1000 μm.

If desired, the mineral support materials can be used in combinationwith organic (nonmineral) additives such as cellulose powders orcellulose fibers and also powders or fibers of organic polymers(polyacrylonitrile, polystyrene, etc.).

The invention also provides a process for preparing the pulverulentpolymer compositions, which is characterized in that the polyethercarboxylate is incorporated into the respective mineral support materialimmediately after the polymerization process for preparing the polyethercarboxylate. The polymer is preferably introduced into the initiallycharged and, if desired, preheated mineral support material in as finelydivided a form as possible, with the polyether carboxylate being a bulkpolymer or being able to be in the form of an aqueous solution, aninverse emulsion or a suspension.

In a preferred embodiment, a polyether carboxylate prepared by bulkpolymerization at from 110 to 140° C. is sprayed at a temperature in therange from 70 to 120° C. onto a preheated mineral support material (forexample of the silica type) in a mixer.

Particularly effective incorporation with very low consumption ofmineral support material can be achieved by applying the polyethercarboxylate as a mist onto the preheated support material. Theeffectiveness drops when the polymer is sprayed, dripped or poured ontothe support material, because the surface area of the substance to beincorporated decreases in that order.

Furthermore, the mixing technique in the incorporation is of particularinterest and depends very strongly on the type of support material used.

Support materials having a pronounced porous structure, e.g. silicas,have a particularly high adsorption capacity.

Mixers in which high shear forces occur near the mixing devices candestroy the porous structure, as a result of which polyethercarboxylates present in the voids can be squeezed out again. It istherefore advisable to use mixing apparatuses in which low shear forcesoccur, e.g. drum mixers, V mixers, tumble mixers or otherrepresentatives of free-fall mixers, for this type of support.

Further suitable mixers for porous supports are cone mixers, plowsharemixers or spiral mixers having vertically or horizontally installedmixing elements. In the case of mineral supports whose structure cannotbe destroyed by the mixing process, all other types of apparatus, e.g.dissolvers, screw mixers, twin-screw mixers, air-mix mixers and others,are also usable.

Finally, it is possible within the scope of the present invention tofollow the incorporation of the polyether carboxylate into the supportby a drying process so as to increase the productivity of the supportmaterial.

The invention further provides for the use of at least one pulverulentpolymer composition according to the present invention in buildingmaterials, suitable building materials being bitumen products, such asasphalt, bituminous adhesive, sealing, knifing and paint or coatingcompositions (rooftop parking areas), or products based on hydraulicallysetting binders such as cement or based on latent hydraulic binders suchas fly ash and trass, such as mortar (casting mortar), screeds,concrete, plasters and renders, adhesive, sealing and knifingcompositions and also paints. A further group of possible buildingmaterials comprises gypsum-based building materials (mortar, plaster,screed), anhydrite-based building materials, the other buildingmaterials based on calcium sulfate, the group of ceramic compositions,refractory compositions and oilfield materials. Finally, the polymercompositions of the invention can also be used in dispersion-basedbuilding materials such as dispersion tile adhesives, elastic sealingslurries, foundation coatings, mortar adhesion additives and pulverulentinterior and exterior wall paints.

The pulverulent polymer compositions of the invention can also be usedin combination with the abovementioned groups of building materials,e.g. in bitumen-containing cement screeds, casting mortars, etc.

The incorporation of the pulverulent polyether carboxylates into thebuilding material is generally carried out together with that of otherfillers and building material additives, such as dispersion powders,water retention improvers, thickeners, retardants, accelerators, wettingagents, etc. The proportion of polyether carboxylate is usually from 0.1to 5% by weight, based on the weight of the building material. Thepulverulent polymer compositions of the invention have a series ofadvantages compared to polyether carboxylates obtained in powder form byconventional means. This will be illustrated by the following examples.

EXAMPLES Example 1

In a tumble mixer from Bachofen AG, Basle, a pulverulent polymercomposition consisting of 75 g of a precipitated silica having aspecific surface area of 190 m²/g and preheated to 80° C. and 425 g of amolten polyether carboxylate (A) is prepared at 80° C. by mixing for 75minutes.

The polyether carboxylate (A) was prepared by solvent-freepolymerization as follows:

50.1 g of maleic anhydride (0.51 mol) are esterified with 294 g ofmethylpolyethylene glycol 1150 (0.256 mol) at a temperature of 120° C.for 3 hours with careful exclusion of atmospheric oxygen. 72.8 g ofstyrene (0.7 mol) containing a small amount of n-dodecyl mercaptan and8.3 g of azobisisobutyronitrile dissolved in 50 ml of acetone wereintroduced as separate feed streams at 110° C. over periods of 90 minand 120 min respectively into the initial mixture obtained in this way.The reaction vessel was continually flushed with nitrogen so that muchof the acetone could be driven out even during the feed stream additionphase. In a 2-hour after-reaction at 120° C., the remaining acetone wasremoved to give a light-yellow bulk polymer of maleic anhydride, styreneand methylpolyethylene glycol 1150 monomaleate in a molar ratio of0.5:1.37:0.5 (polyether carboxylate A). After addition of 0.5% by weightof an antioxidant and spraying onto the abovementioned mineral supportmaterial and mixing for 75 minutes, a sticking- and caking-resistant,free-flowing, ivory-colored powder having an active content of polyethercarboxylate of 85 percent by weight (mean particle diameter: 39 μm) wasobtained.

Comparative Example 1

In accordance with the prior art, the bulk polymer synthesized inExample 1 was cooled to 80° C. and stirred into 425 g of water. Afterthe aqueous solution obtained had cooled, the pH was set to 8.5 by slowaddition of dilute aqueous sodium hydroxide. 0.5% by weight, based onthe polymer content, of an antioxidant was stirred in, and the polymersolution was, for viscosity reasons, diluted with water to 30% by weightbefore being converted into a powder in a laboratory spray dryer fromNIRO. This gave a light-brown powder which had a mean particle diameterof 54 mm [sic] and had a very strong tendency to form lumps.

The powders obtained in the examples were characterized in respect ofthe following data:

1. Polymer content (GPC)

2. Flow behavior of the powders (outflow from a vessel with a bottomoutlet)

3. Caking resistance of the powders (under 2 kg pressure)

4. Fluidizing effect in a cement building material mixture

Examples 2 to 9

These were carried out using the procedure described in Example 1, butthe following finely divided mineral support materials were used inplace of the silica used there (Table 1):

TABLE 1 Proportion Support by weight Specific of surface Polymer/ areaSupport Example Type (m²/g) (%) 2 chalk 11 40:70 3 dolomite (micronized)4 45:55 4 kieselguhr 65 55:45 5 calcium silicate 35 70:30 6 aluminumsilicate 100 50:50 7 sodium aluminum silicate 80 65:35 8 precipitatedsilica 450 80:20 9 precipitated 450 75:25 silica/chalk (1:1) 11

Examples 10 to 15

In place of the polyether carboxylate obtained by solvent-freecopolymerization which was used in Example 1, the following polymerswere used (Table 2):

TABLE 2 Weight ratio of polymer/ Ex- Polyether support¹⁾ amplecarboxylate²⁾ Type of synthesis (%) 10 B bulk polymerization 87:13 11 Cbulk polymerization 90:10 12 D bulk polymerization 81:19 13 E bulkpolymerization 80:20 14 F bulk polymerization 75:25 (graftpolymerization) 15 G aqueous solution 67:33 polymerization ¹⁾Support:precipitated silica (specific surface area: 190 m²/g) ²⁾Polymercompositions: B Maleic anhydride-styrene-methylpolyethylene glycol 2000monomaleate copolymer (molar ratio = 0.60:1.37:0.40) C Maleicanhydride-styrene-methylpolyethylene glycol 5000 monomaleate copolymer(molar ratio = 0.73:1.37:0.27) D Maleic anhydride-allylpolyethyleneglycol 1100 monoethyl ether copolymer (molar ratio = 1.15:1) E Maleicanhydride-vinylpolyethylene glycol 500 monomethyl ether copolymer (molarratio = 1.10:1) F to 50 mol %-esterified graft copolymer ofmethylpolyethylene glycol 500 and maleic anhydride (molar ratio = 1:1.6)G Maleic acid-ethylene glycol monovinyl ether-methylpolyethylene glycol2000 monoethyl ether copolymer (molar ratio = 0.40:0.85:0.37), solidscontent = 45%, sodium salt, pH = 6.5)

Comparative Examples 2 to 7

The polyether carboxylates B to G listed in Examples 10 to 15 werediluted, neutralized, provided with an antioxidant and converted intopowder by means of spray drying using the procedure indicated inComparative example 1.

The test results obtained from Examples according to the invention 1 to15 and Comparative examples 1 to 7 are summarized in the following useexamples.

Use Example 1 Polymer Content of the Pulverulent Polymer Compositions inthe Examples According to the Invention and the Comparative Examples

The polymer content was determined by gel permeation chromatography(conditions: Waters (Milford, Mass.); Shodex OH Pak KB-804 and KB-802.5;standard: polyethylene glycol; eluant: NH₄ ⁺HCOO/CH₃CN 80:20 v/v).

It has been found that direct conversion of the polymers as described inExamples 1 to 15 into powders is not associated with a reduction in theactive polymer content. In contrast, in the case of polymers whichcontain ester bonds and have been converted into powders by methodsaccording to the prior art, the polymer content after spray drying issignificantly reduced. This is attributable to part of the polyetherconstituents bound via ester groups in the polyether carboxylates in theform of comb or graft copolymers being split off in the dilution,neutralization and spray drying process.

TABLE 3 Polymer content²⁾ (% by weight) Polyether after in the Examplecarboxylate¹⁾ polymerization powder Example 1 A 89.7 89.6 Example 2 A88.9 88.7 Example 6 A 87.4 87.6 Example 8 A 86.6 86.7 Example 9 A 88.088.0 Comparison 1 A 89.2 79.4 Example 10 B 82.2 83.0 Comparison 2 B 81.773.6 Example 11 C 79.5 79.5 Comparison 3 C 79.2 70.0 Example 14 F 90.490.3 Comparison 6 F 90.3 83.8 ¹⁾Polymer composition as per Example 1 andTable 2 ²⁾GPC

Use Example 2 Powder Flow Behavior of the Polymer Compositions Accordingto the Invention and of Comparative Polymers

The powder flow (without application of pressure) was determined by themethod of K. Klein: Seifen, Öle, Fette, Wachse 94 (1968), page 12, forvarious polymer compositions. For this purpose, silicone-treated glassvessels with a bottom outlet and different outlet diameters were filledto the brim with the test substance. For the evaluation, grades wereassigned on the scale from 1, i.e. the powder flowed from the vesselwith the smallest outlet opening (ø=2.5 mm) without stopping, to 6, i.e.the powder does not flow even from the vessel with the largest opening(ø=18 mm). The measurements for each powder were commenced using thevessel with the largest outlet opening.

TABLE 4 Powder flow Polyether Evaluation grade for Example carboxylate¹⁾powder flow Example 1 A very good (1) Example 2 A good-satisfactory(2-3) Example 3 A satisfactory (3) Example 4 A good (2) Example 5 A good(2) Example 6 A good (2) Example 7 A very good (1) Example 8 A very good(1) Example 9 A good (2) Comparison 1 A unsatisfactory (6) Example 10 Bvery good (1) Comparison 2 B poor (5) Example 11 C very good (1)Comparison 3 C sufficient (4) Example 12 D good (2) Comparison 4 Dunsatisfactory (6) Example 13 E satisfactory (3) Comparison 5 Eunsatisfactory (6) Example 14 F good (2) Comparison 6 F sufficient (4)Example 15 G satisfactory (3) Comparison 7 G sufficient (4) ¹⁾polymercomposition as per Example 1 and Table 2

Use Example 3 Caking Resistance of Polymer Compositions According to theInvention and of Comparative Polymers

Pulverulent products tend to cake when stacked in bags or in a hopper.To assess the caking resistance or “stackability”, the powder to betested was introduced to a height of about 20 mm into a steel cylinderhaving an internal diameter of 50 mm and loaded by means of a punchhaving a weight of 1.2 kg and a loading weight of 2 kg.

The pressure prevailing in this test arrangement is 0.17 kg/cm², whichcorresponds to the pressure of from 10 to 12 bags having a weight of 50kg stacked on top of one another. After loading for 24 hours, theloading weight was removed and the powder pellet was ejected from thecylinder. The hardness of the powder pellet is regarded as a criterionfor the caking resistance according to the following assessment scheme.

TABLE 5 Assessment Grade Behavioral feature very good 1 completelyunchanged good 2 adheres slightly, disintegrates into the original statesatisfactory 3 loosely shaped, disintegrates into a powder under gentlefinger pressure sufficient 4 loosely caked, just still disintegratespoor 5 semifirmly caked, no longer disintegrates unsatisfactory 6strongly compacted

The following results were obtained:

TABLE 6 Polyether Evaluation code for Example carboxylate¹⁾ cakingresistance 1 A good (2) comparison 1 A sufficient (4) 10 B good (2)comparison 2 B poor (5) 11 C good (2) comparison 3 C satisfactory (3) 12D good (2) comparison 4 D sufficient (4) 13 F good (2) comparison 5 Fsufficient (4) 15 G good (2) comparison 7 G satisfactory (3) ¹⁾Polymercomposition as per Example 1 and Table 2

Use Example 4 Fluidizing Effect in a Cement-containing Building Material

The powder obtained from the examples according to the invention andfrom the comparative examples were examined in respect of their useproperties in a mortar formulation. For this purpose, the pulverulentpolymer compositions were mixed dry with the amounts of sand andPortland cement (CEM I 42.5 R Kiefersfelden) prescribed in accordancewith DIN 1164 part 7. This was followed by addition of water and mixingof the constituents in accordance with the standard. The slump of thefresh mortar was determined for each powder type immediately and after15, 30, 45 and 60 minutes

TABLE 7 Polymer Polyether Slump (cm) Example addition¹⁾ carboxylateimmediately 15 min 30 min 45 min 60 min  1 0.15 A 23.5 22.5 20.1 19.018.3 comparison 1 0.15 A 22.9 19.6 17.4 16.3 15.4 10 0.15 B 25.0 24.122.1 19.3 17.2 comparison 2 0.15 B 24.3 22.0 19.4 17.0 14.0 11 0.20 C26.1 23.6 21.1 19.9 18.4 comparison 3 0.20 C 25.4 21.6 19.9 17.3 14.6 150.15 G 27.9 26.1 24.9 23.9 23.0 comparison 7 0.15 G 26.0 24.0 21.4 20.017.3 ¹⁾In % by weight of polyether carboxylate based on the weight ofcement ²⁾Polymer composition as per Example 1 and Table 2

W/Z=0.45

CEM I 42.5 R Kiefersfelden

1% by weight of tributyl phosphate based on polymer

Due to the loss of polyether side chains, the processability of mortarmixtures containing polymer powders prepared according to the prior artdeteriorates significantly more quickly than that of mixtures containingpulverulent powder compositions according to the invention. This isattributable to the reduced steric stabilization of the cementparticles.

What is claimed is:
 1. A pulverulent polymer composition based onpolyether carboxylates, comprising a. from 5% to 95% by weight of awater-soluble polymer made up of polyoxyalkylene-containing structuralunits, carboxylic acid or carboxylic anhydride monomers; and, b. from 5%to 95% by weight of a finely divided mineral support material having aspecific surface area of from 0.5 m²/g to 500 m²/g as determined by theBET method in accordance with DIN 66 131 and is obtained by sprayingmolten polyether carboxylate onto a mineral support material at atemperature of from 70° C. to 120° C.
 2. The polymer compositionaccording to claim 1, wherein the water-soluble polymer containspolyethylene glycol or polypropoylene glycol groups in its main chain orin its side chain.
 3. The polymer composition according to claim 1,wherein the carboxylic acid or carboxylic anhydride mononers compriseacrylic acid, methacrylic acid, maleic acid, maleic acid anhydride,fumaric acid, itaconic acid or itaconic anhydride.
 4. The polymercomposition according to claim 1, wherein the water-soluble polymerfurther comprises monomers based on vinyl or acrylate compounds.
 5. Thepolymer composition according to claim 1, wherein the support materialis selected from the group consisting of chalk, silica, calcite,dolomite, quartz flour, bentonite, ground pumice, titanium dioxide, flyash, cement, aluminum silicate, talc, anhydrite, lime, mica, kieselguhr,gypsum, magnesite, alumina, kaolin, ground slate and other rocks, bariumsulfate, and mixtures thereof.
 6. The polymer composition according toclaim 1, wherein the mineral support materials are used in combinationwith at least one organic additive.
 7. The polymer composition accordingto claim 1, wherein the support materials have a particle size of from0.1 μm to 1000 μm.
 8. A process for preparing the polymer compositionaccording to claim 1, comprising incorporating the polyether carboxylateinto the mineral support material immediately after the polymerizationof the polyether carboxylate.
 9. The process according to claim 8,wherein the polyether carboxylate is a bulk polymer.
 10. The processaccording to claim 8, further comprising spraying molten polyethercarboxylate onto a preheated mineral support material at a temperatureof from 70° C. to 120° C.
 11. The process according to claim 8, whereinthe polyether carboxylate is incorporated into the mineral supportmaterial in the form of an aqueous solution, an inverse emulsion or asuspension.
 12. The process according to claim 8, wherein said supportmaterial has a porous structure, and said polyether carboxylate isincorporated into said support material by using a mixer which produceslow shear forces.
 13. A method for making a building material,comprising combining from 0.1% to 5% by weight of the pulverulentpolymer composition of claim 1, with a pre-existing building material.14. The method of claim 13, wherein said pre-existing building materialis a bitumen product, a building material based on hydraulically settingbinders, a gypsum based product, a calcium sulfate based product, aceramic composition, a refractory composition, an oil field material, ora dispersion based material.
 15. The method of claim 13, furthercomprising adding at least one of building material additive or a fillercomponent.
 16. The method of claim 14, wherein said additive is adispersion powder, a water retention improver, a thickener, a retardant,an accelerator or a wetting agent.
 17. The pulverulent polymercomposition of claim 1, wherein said water soluble polymer comprises anadditional monomer.
 18. The pulverulent polymer composition of claim 1,wherein said additional monomer is a carboxylic acid monomer, or acarboxylic anhydride monomer.
 19. The polymer composition of claim 5,wherein said cement is Portland cement or blast furnace cement.
 20. Thepolymer composition of claim 6 wherein said at least one organicadditive is a cellulose powder, a cellulose fiber, an organic polymerpowder or an organic polymer fiber.
 21. The process according to claim12, wherein said mixer is a free fall mixer.
 22. The method of claim 14,wherein said hydraulically setting binder is cement or a latenthydraulic binder.
 23. The method of claim 14, wherein said calciumsulfate based product is a calcium sulfate anhydrite.